Dozens of protesters, including the president of the AFL-CIO, were arrested yesterday for obstructing the sidewalk in front of a New York University library, capping a demonstration held to pressure the university administration to negotiate with the union representing NYU graduate assistants.

Labor groups staged the noisy demonstration in front of the Bobst Library at the Washington Square campus as time ran out on NYU’s contract with a union that represents the graduate student assistants. Some well-known figures attended, such as AFL-CIO president, John Sweeney; the television actress Morgan Fairchild, a union activist; the president of the United Federation of Teachers, Randi Weingarten; State Senator Thomas Duane of Manhattan, and a mayoral candidate, Gifford Miller.

The protest appeared unlikely to change the bleak reality facing the United Auto Workers union, which represented about 1,000 NYU graduate teaching and research assistants until today. NYU was the only private university in America to have a union of graduate students.

NYU officials said yesterday that they are unwilling to budge from their position that the graduate assistants are students, not employees, and therefore should not be eligible for collective bargaining. They are preparing for the strong possibility that some of their graduate students will go on strike in the fall semester, which begins Tuesday.

Fewer people showed up for the rally than union officials had predicted. The number of demonstrators looked to be between 500 and 600, while Local 2110’s president, Maida Rosenstein, said Tuesday she thought 1,000 people would turn out.

Fewer than 100 NYU graduate students joined yesterday’s rally. The other participants were a mixture of graduate students from other schools, including Columbia and Yale universities, and hundreds of employees from at least a half-dozen labor unions. They marched back and forth between rows of metal barriers set up on the street, with about 40 New York City police officers on hand to keep things orderly.

One NYU undergraduate, Irene Walcott, held a sign that read: “Bush: Iraq has WMDs. NYU: Graduate students are not workers. Don’t be fooled.”

It was a humid day, and NYU officials outside the library provided bottles of cold water and granola bars to protesters.

Mr. Sweeney told The New York Sun that NYU has “slowly become an anti-union and anti-worker administration.” He said the graduate students “have the right to strike” and the school’s administration ought to be held responsible for any disruptions caused by a student strike.

For about an hour, Ms. Fairchild stood in the middle of the crowd, wearing jeans and looking slightly uncomfortable in the heat. She told the Sun that she disagreed with NYU’s position that the assistants are primarily students.

“When they’re students, they’re students,” she said. “When they’re workers, they’re workers.”

At the end of the demonstration, a cheery Mr. Sweeney, along with other labor leaders and about 10 NYU graduate students, knelt down on the sidewalk in front of the entrance to the library, which houses the offices of NYU’s administration. After police ordered the protesters to move away, officers bound their hands with plastic handcuffs and drove them away in prison wagons. About 10 NYU graduate students were arrested.

NYU officials have argued that the responsibilities that come with being a teaching assistant – such as leading discussion groups, grading papers and exams, and in some cases teaching courses – are an important part of academic training. They have also criticized the UAW, which is part of the AFL-CIO, for filing grievances that administrators said infringed upon the university’s freedom to decide who teaches what courses. When the union objected to hiring decisions made by the university, arbitrators consistently ruled in favor of NYU.

The National Labor Relations Board ruled in July 2004, in a 3-2 decision, that universities are not obligated under federal labor law to pursue collective bargaining with their graduate teaching and research assistants.

The majority of the board reasoned that the graduate assistants are essentially students because their primary responsibility is obtaining their degrees and only a limited amount of time is spent performing teaching and research assistant duties. The stipends that the graduate assistants receive, the board majority found, should be viewed as part of their financial aid.

The board’s decision reversed its 2000 ruling in favor of graduate students’ unions in a case involving NYU. During the period between decisions, Republicans gained a majority of board seats.

After announcing last month its intention to cease recognizing the graduate students’ union, NYU said it would increase the students’ stipends by $1,000 a year over the next three years. This academic year, the base stipend for Ph.D. students is $19,000, and by the 2007-08 year it will be $21,000. NYU said it would also continue to pay 100% of the health insurance premiums of graduate assistants, who do not pay tuition.

NYU graduate students at yesterday’s rally said they were satisfied with stipend levels but wanted to be able to address their grievances to a party independent of the university.

“We need our rights to be articulated and represented outside of NYU,” a Ph.D. student in Hebrew and Judaic studies, Daniella Doron, said.

The director of the Center for Neural Science at NYU, Anthony Movshon, said unionizing graduate students distorts their role in the university.

“To impose a manager-worker relationship just breaks the basic compact that researchers and scholars should have with their students,” he said. “These are my future colleagues.”

The Police Department’s chief spokesman, Deputy Commissioner Paul Browne, said last night that 76 demonstrators were arrested. They were issued desk appearance tickets and then released, Mr. Browne said.